An A-frame is a item of BDSM furniture designed to tie a person to. It consists of a large triangluar frame about 7 feet tall and 2-3 feet wide. The space inside the triangle is usually filled with a lattice work of rope or horizontal steel bars. A-frames are either secured to a wall or mounted on a sturdy base; as with other types of furniture, it is vital that the base be stable enough to prevent toppling even if the captive struggles violently.
In function, an A-frame falls between a whipping post and a St Andrews cross. The captive is usually bound with their hands together, above their head to the apex of the frame. The legs are spread apart and secured to the bottom two corners. For more secure bondage, the captive's limbs and torso can be tied to the rope lattice or bars in the centre of the frame.
Depending on how the captive is bound, the A-frame puts less stress on the person's body than a St Andrews cross, allowing for longer periods of bondage. The person can be bound either facing the frame (for a flogging) or with their back to the frame (for torture or tease and denial). The feeling of being bound to an A-frame is not as intense as being bound to a cross (for both captor and captive), but the fact that the bound person can be left for longer allows forms of play that would be difficult to do on a cross.